The present invention relates to a structure of thermal reactors for use in an exhaust gas cleaning device of an internal combustion engine mounted on cars or other vehicles. More specifically, this invention aims at a provision of novel thermal reactors, particularly regarding manifold type ones collecting exhaust gas from a plurality of engine cylinders, provided with an external shell and an internal shell (core) and having to be so constructed as to receive a part of exhaust gas from some of cylinders at a certain angle less than 90.degree. with the axis of the reactor due to the requirements of cylinder arrangement, which permit the thermal expansion of the core and yet perfectly maintain the tightness of exhaust gas.
Manifold type thermal reactors whereinto exhaust gas is collected from a plurality of engine cylinders to effect a high temperature oxidization reaction of the harmful HC, CO gases for discharging the same as harmless substances CO.sub.2, H.sub.2 O by utilizing the thermal energy of the exhaust gas itself have been known. These known reactors are provided with an external shell of cast iron and internal shell (called a core) of stainless steel.
Conventional reactors are required to be constructed, in many cases, to effect space saving or to conform to available space with the reactor positioned, with respect to some cylinders at an angle of less than 90.degree. and greater than 0.degree.. In these cases the thermal expansion often caused difficulties because of the fact that parts of the apparatus had different thermal expansion characteristics.